The invention relates generally to medical imaging systems, and more particularly, to Computed Tomography (CT) systems.
Lung Cancer is a leading cause of cancer related mortality in the United States. Many references in the literature point to a need for better patient management to provide earlier detection. Early detection is also important for reducing mortalities for other lung diseases, such as Chronic Obstructive Pulmonary Diseases (COPD). Conventional techniques to detect cancer include use of medical imaging systems such as X-ray, CT scan, and the like. CT imaging provides an image of anatomy in detail and is therefore being increasingly used for detecting and following the evolution of, for example, lesions that may be potential cancers, as well as other diseases.
In the case of CT image data, lung segmentation allows focusing on the lung area only and is an important preprocessing step. Several methods are used to analyze the segmented lung area in order to detect abnormalities. One of the methods used is Advanced Lung Analysis (ALA). Radiologists use ALA to search for nodules in the segmented lungs. The ALA method typically includes a digital contrast agent (DCA) algorithm, which is directly applied on the lung Region of Interest (ROI) scan data. The sensitivity and specificity of the DCA algorithm is directly linked to the performance of the lung segmentation algorithm.
For Chronic Obstructive Pulmonary Diseases (COPD), lung and trachea segmentation are processes without which assessment of the disease is very difficult, if not impossible. For example, for automatic emphysema quantification, lung segmentation is used to focus on the parenchyma only. Lung segmentation allows for an automated emphysema quantification metric, and for its follow-up over time, as well as having density histograms that incorporate the lung area only. Lung segmentation can then be performed for both lungs, or for each lung or lobe separately. As another example, for automated virtual bronchoscopy, automated trachea data extraction provides a fully automated tool to initiate a tubular tracking in the bronchi, and which may be performed using techniques similar to those of General Electric's Advanced Vessel Analysis software.
For Radiotherapy planning, performed physicians need to be able to delineate the lungs very accurately to efficiently position the radiotherapy beams with a separate delineation so as to minimize, for example, radiation exposure and possible collateral damage to other organs. Moreover, if the CT scan is a full body image scan, it becomes difficult for the physicians to exactly pinpoint and delineate the lungs. Also, to perform analysis over a particular growth of a nodule over a time typically requires segmentation to the level of internal structures of the lungs.